1. Field of the Invention
The present invention relates to an actuator apparatus, and more particularly, to an actuator, which is used in an optical communications system or the like, and which, for example, is applicable to a driven-type mechanical optical switch, for arranging a pair of optical fibers by aligning them with an optical axis, and moving either a mirror or a shielding plate in and out of the gap therebetween.
2. Description of the Related Art
In recent years, actuator apparatus capable of achieving high-speed, high-precision displacement are desired for use in optical switching devices and so forth in optical transmission systems, such as optical LAN (local area networks) in particular. In order to apply these actuator apparatus to optical switches in particular, the actuator apparatus must have a moving speed of about eleven to nineteen milliseconds, and must possess accuracy of around xc2x11 xcexcm, and various methods for achieving this have been proposed. Among these systems, the mechanical optical switch is advantageous in that, since the direction of propagation of direct light can be changed by mechanically driving a fiber or mirror (or shielding plate) using a mechanical switch, there is less loss of light and cross-talk inside the switch than there is with optical switches of other systems, and commercialization of mechanical optical switches is being pushed forward as the most promising technology capable of being applied to optical switches.
As mechanical optical switching technology in this technical field, a mirror drive-type mechanical 2xc3x972 optical switch is disclosed in Japanese Patent Laid-open No. 2001-75026. This prior art will be explained using a diagram of the prior art.
First, the optical fiber portion constituting an optical switch will be explained initially. In this optical fiber portion, there is disposed a first collimator lens assembly 105, which arranges a pair of optical fibers 101, 103 symmetrically with the optical axis of the lens, and a second collimator lens assembly 111, which arranges a pair of optical fibers 107, 109 symmetrically with the optical axis of this collimator lens, and these first and second collimator lens assemblies 105, 111 are placed opposite one another, and their optical axes are aligned. At this time, the first and second collimator lens assemblies 105, 111 are arranged such that optical fiber 101 and optical fiber 109, and optical fiber 103 and optical fiber 107 mutually cross over to form optical connections, and these assemblies are supported by alignment block 113. Then, the above-mentioned first and second collimator lens assemblies 105, 111 are constituted from a pair of optical fibers not shown in the figure, and a ferrule for supporting the optical fibers, and an approximately 0.25-pitch rod lens, which is connected to the optical fibers and ferrule tip.
Next, the actuator apparatus in the prior art will be explained. A shaft opening provided parallel to the optical axis of the lens is disposed in the above-mentioned alignment block 113, and a reflecting mirror shaft 115 is inserted into this shaft opening.
Since a reflecting mirror 117 must accurately reflect light being emitted from the above-mentioned optical fibers 101, 103, a reflecting mirror reference plane 119 is machined into the alignment block 113 perpendicular to the optical fibers, and reflecting mirror 117 makes contact with the surface of this reflecting mirror reference plane 119, and its perpendicularity is defined. According to this constitution, it is a state in which the surface of the reflecting mirror 117 is made perpendicular to the optical axis of the above-mentioned optical fibers, and the reflecting mirror 117 can rotate together with the above-mentioned reflecting mirror shaft 115.
In addition, this reflecting mirror 117 is capable of moving between a first position, in which the reflecting mirror 117 is perpendicular to the optical axis of the lens at the lens focal plane, and reflects light from the respective optical fibers, and a second position, in which the reflecting mirror 117 allows light to pass through, and this operation is carried out by a motor (DC micromotor 121), which is driving means. This specific driving means is capable of arbitrarily moving the above-mentioned reflecting mirror 117 from the first position to the second position having the above-mentioned reflecting mirror shaft 115 as the supporting point, in accordance with a bushing 123 and an eccentric pin 125 mounted to the motor shaft of DC micromotor 121.
Further, since the above-mentioned reflecting mirror 117 is precisely moved in and out of the gap of the above-mentioned pair of optical fibers 101, 103 by the above-mentioned actuator apparatus, a mechanism is required to define the above-mentioned first position and second position. This mechanism is constituted such that the above-mentioned eccentric pin 125 is inserted into a notched groove 127 (for example, a V shape) formed in a specified shape in the above-mentioned alignment block 113, and the constitution is such that rotating the above-mentioned motor shaft in one direction determines the first position by bringing this eccentric pin 125 into contact with a face of this notched groove 127, and, in addition, rotating the motor shaft in the other direction determines the second position by bringing this eccentric pin 125 into contact with the opposite face of the notched groove 127.
Furthermore, a permanent magnet 129 is embedded inside the alignment block 113 in a location close to the reflecting mirror shaft 115, and by virtue of this permanent magnet 129 biasing reflecting mirror shaft 115, which comprises a magnetic substance, in one direction in the first position, at which light from the optical fibers is reflected, the slow moving mirror rotation shaft 115 is constantly set in the same position. Accordingly, in addition to causing the light emitted from the optical fibers to be accurately reflected, subsequent to moving the reflecting mirror 117 to the intended position, the position of this reflecting mirror 117 can be maintained as a self-hold state, wherein this position is held by the magnetic attracting force of the permanent magnet 129 without energizing the DC motor 121.
Combining a conventional actuator apparatus constituted in this manner with the above-mentioned optical fiber portion realized the moving speed and precision of the actuator apparatus of the above-mentioned optical switch, and resulted in a compact mechanical optical switch, which also featured good repeatability, and was not susceptible to the effects of external forces, such as vibrations and impacts.
Furthermore, the above-mentioned reflecting mirror 117 was constituted by coating a metal base material, such as a stainless steel, on both sides with Tixe2x80x94N of a hardness of MHv 1800 or greater, and, in addition, attaching a high reflectivity coating of gold (Au), platinum (Pt) or the like via either sputtering or electroless plating.
However, although a conventional actuator apparatus excels from the aspects of moving speed and precision, it has the following disclosed problems.
To operate an optical switch normally, conventional actuator apparatus specified the perpendicularity of the reflecting mirror 117 by causing surface contact between the alignment block 113 and the reflecting mirror 117, and moved the reflecting mirror 117 in and out of the optical fiber portion in a state, wherein the reflecting mirror 117 was constantly perpendicular to the optical axis of the above-mentioned optical fibers. However, when rotating this reflecting mirror 117 between the first position and the second position, this reflecting mirror 117 had to be rotated as-is with surface contact between the alignment block 113 and reflecting mirror shaft 115, and between the alignment block 113 and the reflecting mirror 117. Accordingly, there are problems from the standpoint of long-term reliability in that, when an optical switch is operated for a long period of time by rotating this reflecting mirror 117, there are times when, due to the friction of the above-mentioned surface contact, the reflecting mirror shaft 115 supporting this reflecting mirror 117 gradually slips out of position, or the perpendicularity of the reflecting mirror 117 is lost, enabling the assumption that it will become impossible to accurately reflect the light emitted from the optical fibers.
Further, conventional actuator apparatus must use a powerful permanent magnet 129 to attract the reflecting mirror shaft 115, which has a large moment of inertia, in order to achieve the above-mentioned self-hold state, and to suppress slight changes in the reflecting mirror resulting from external shocks. The constitution is such that, even when the reflecting mirror 117 is moved between the first position and the second position, it is driven while the permanent magnet 129 attracts the reflecting mirror shaft 115 as-is. For this reason, it should come as no surprise that during the movement, the DC micromotor 121 must overcome the attracting force of this permanent magnet 129, and must constantly generate enough force to enable the reflecting mirror 117 to move. Therefore, the torque of the DC micromotor 121 must be made sufficiently large, resulting in high power consumption.
An object of the present invention is to provide a compact actuator apparatus that is capable of achieving stable repeatability even when driven for a long period of time, and moreover, features excellent durability, and can also perform driving at low power consumption.
To achieve the above object, the present invention will employ a technological constitution such as that disclosed hereinbelow.
To solve for the above-mentioned problems, a first aspect of the present invention has a constitution, which comprises a rotating body comprising a rotating shaft supported in a freely rotating condition, and a rotor magnet affixed to this rotating shaft; driving means for rotationally driving this rotating body; and at least one yoke, which forms a closed magnetic circuit connecting the poles of the rotor magnet, and which carries out self-hold relative to the rotating body in a prescribed rotational position. Further, a second aspect of the present invention has a constitution, which comprises a rotating body comprising a rotating shaft supported in a freely rotating condition, and a rotor magnet affixed to this rotating shaft; first defining means for defining the rotating body to a first rotational position; second defining means for defining the rotating body to a second rotational position; driving means for rotationally driving the rotating body between first defining means and second defining means; and at least one yoke, which forms a closed magnetic circuit between the poles of the rotor magnet in a rotational position of at least one side of the first rotational position or the second rotational position, and which carries out self-hold relative to the rotating body in this rotational position.
Here, at least one of the rotor magnet or yoke is a permanent magnet, and the other is an electromagnet, and the rotating body is subjected to self-hold by the magnetic force of the permanent magnet.
Further, driving means comprises either at least one exciting coil disposed in at least one yoke, or an exciting coil disposed in the rotor magnet, and uses either one of the exciting coils to rotate the rotating shaft via a magnetic attracting action and/or a magnetic repulsing action acting between the yoke and the rotor magnet.
Further, defining means comprises a member for determining a rotational position by either making contact with a portion of the rotating body or using a magnetic attraction at a rotational position defined by defining means. When the rotational position determining member makes contact with the rotating body, it can be constituted by a striking member.
Further, a yoke can be constituted by either integrating or combining the respective magnetic materials of a rotational position determining member arranged so as to make contact with or to be magnetically attracted to one pole of the rotor magnet at a prescribed rotational position, and another rotational position determining member arranged so as to make contact with or to be magnetically attracted to the other pole of the rotor magnet.
Further, the rotor magnet is polarized at two poles either perpendicular to or in parallel with the direction of the rotating shaft, and can carry out self-hold relative to the rotating body by forming a closed magnetic circuit between itself and the yoke, and further, and can rotate the rotating body by generating magnetic attractions and magnetic repulsions between itself and the yoke, carrying out switching. Further, the rotating body and rotational position determining members can be made into shapes, which enable them to make surface contact with one another, thereby making it possible to increase the self-hold force.
Further, the rotating body comprises a driven body, which is inserted and removed from the gap of a pair of optical fibers, at least one part of which is aligned with the optical axis, in accordance with the rotation of this rotating body, and the conduction of light between optical fibers is controlled by this driven body. Here, the switching of light is performed by disposing a reflective surface on the driven body, and reflected the light by virtue of this reflective surface. By forming the reflective surface perpendicular to the rotating body, light can be switched between pairs of optical fibers, which are arranged parallel to the rotating shaft.
Further, by making the constitution such that either the center of gravity of the rotor magnet and center of gravity of the above-mentioned rotating shaft approximately correspond, or the center of gravity of the rotor magnet and shielding plate and center of gravity of the rotating shaft approximately correspond, it is possible to reduce drift resulting from angular moment when the actuator is acted on by an external force.
Further, by providing a shielding plate in a position that is symmetrical to the reflective surface relative to the rotating body, and providing a position detecting portion for detecting the rotational position of the rotating body corresponding to the operation of this shielding plate, it is possible to control conduction to the exciting coil by providing the output from this position detecting portion as feedback.